The present invention relates to method and system for controlling a fluid transportation system by a water pipe network or a gas pipe network. By way of a specific example, a waterworks pipe network system is explained below.
A water supply system of the waterworks pipe network system (hereinafter simply referred to as a pipe network) includes a reservoir as a water supply, a plurality of demand nodes fed from the reservoir and a plurality of pipe networks connecting the reservoir with the plurality of demand nodes. The water supply control in the waterworks pipe network controls openings of valves and pressures of pumps in the pipe networks such that distributions of flow rate and pressure in the pipe network are maintained at desired distributions even when demand volumes at the demand nodes in the pipe network vary. In a prior art water supply control, an operator merely controls the valves and the pumps in accordance with an instruction manual in case of water shortage or failure. The operator is requested to supply the water with no less than a predetermined pressure in the high demand periods in the morning and in the evening. In order to meet the requirement, the operator supplies the water with a higher pressure than is normally required. In a low demand period in the night, the pressure in the pipe network rises and water leakage thereby amounts to one sixth of total amount of water supplied. In recent years, the price of the water has risen, and from a view point of energy saving, the water supply with a high pressure is not sufficient to resolve the problem. Accordingly, the water supply control in which the pressure in the pipe network is maintained at an appropriate pressure by finely controlling the valves and the pumps to comply with the variation of the demand such that the water is supplied with a necessary pressure in the high demand period and unnecessary pressure rise is suppressed in the low demand period to prevent the water leakage or the failure, has been desired.
The pipe network to be controlled includes no on-line sensor which directly senses the demand volume from time to time but includes monitoring sensors (pressure gauges or flow gauges) at only a certain number of points, for example, several tens of points in the pipe network having several hundreds of pipe lines or demand nodes.
It may be possible to control the water supply such that the pressures at the demand nodes at which the sensors are located are kept at a constant pressure in accordance with the outputs of the sensors. In this case, however, there is no assurance that the pressures at the demand nodes at which the sensors are not provided are kept at the constant pressure.
It may also be possible to arrange the sensors at all of the demand nodes. However, since the sensors and communication equipment for transmitting the data of the sensors are expensive, the number of the measuring points by the sensors must be limited in practice.
It may also be possible to utilize outflow meters provided at the demand nodes, but since the outflow meters are checked once a month, it is not possible to detect the variation of demand from time to time in a day.